Attic Wiring and Capacity

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  #1  
Old 06-27-04, 08:07 AM
Bob C
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Attic Wiring and Capacity

I'll be running a 6/3 wire from the panel to the kitchen going through the attic, a 25 foot run. Is there any requirement on running wire in an attic? I have run a couple of new circuits and rerouted some existing wire in the attic. I pulled this wire straight and tight and attached it to the roofing trusses. Please don't tell me it should be in some kind of conduit. The existing wiring was simply run along the floor of the attic and over joists and than covered with insulation, nothing was tacked down.

Second question has to do with capacity. The home is 1400 sq ft. and has 100 amp service. The new range will be 50 amp, I added HVAC and this added a 30 amp circuit. I will also be adding an above range microwave and will add a dedicated 15 amp circuit. I may also be adding a dishwasher and possible garbage disposal. The dryer in the home is electric on a 30 amp circuit. There are 3 20 amp circuits and a total of 7 15 amp circuits.
If capacity is a problem, I could go change to a gas range.


Thanks for the help.
 
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  #2  
Old 06-27-04, 08:42 AM
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Yes, there are a lot of rules about running cable in an attic. But the rules are different depending on whether attic access is provided by a fixed ladder or stairs, or whether you need to get the ladder out of the garage to get up there.

Basically you need to protect the cable against getting stepped on. When running parallel to the framing members, you can just staple the cable to the side of the framing member. When running perpendicular to the framing members, you need to install a 2x4 and staple the cable to the side of the 2x4. If there is a fixed ladder or stairs, this needs to be done everywhere. If not, this only needs to be done within 6 feet of the opening.

To do the demand load calculation we need more information:
  1. How many tons of air conditioning?
  2. Is the home heat gas or electric? If electric, how many KW?
  3. Is the water heater gas or electric?
  4. Any other big users? Jacuzzi tub? Pool? Welder?
 
  #3  
Old 06-30-04, 07:28 AM
Bob C
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Thanks for the attic info, I think I am fine.

The other items on the load factor:

A/C is 3 tons, heat and hot water are both gas, no other major load items.

Thanks for the help.

Bob
 
  #4  
Old 07-01-04, 05:02 PM
Kray
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I found John's reply (and many others by him) very informative, and have a few follow-up questions. In my case, there is no fixed ladder or stairway to attic. My questions:

1. Given that cable within 6' of the attic entrance should be stapled to side of the framing members, I was wondering what is the proper location for junction boxes? Should they also be mounted to the side of a framing member, or can they be mounted to the top of the framing member? I have a recent DIY job that I need to make some corrections to in that I stapled the romex to the top of the framing member and also mounted (with screws) a couple of metal junction boxes to the top. Fortunately, I can go back and re-position the romex to the sides pretty easily and was wondering if I should also move the J-boxes?

2. I would appreciate clarification on rules (if any) for distances beyond 6' of the attic entrance. For example, several years ago a contractor ran a new circuit through my attic from the main panel to a new patio room addition.
The new room is on the far opposite corner of the house from the panel. The contractor simply ran the romex diagonally through the attic (neither parallel nor perpendicular to framing members) and did not staple it. Possible good news is that none of this circuit is within 6' of the attic entrance. Where does this situation fit on a range from being a rule violation, to sloppy but OK, to perfectly fine? I'm essentially wondering if it's worthwhile to add a couple of junction boxes and lengthen this circuit in order to make it run "squarely" in the attic?
Thanks
 
  #5  
Old 07-01-04, 06:30 PM
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1. Put the boxes anywhere out of harms way. I normally like to mount them where they won't get covered up by insulation so you can find them.

2. There are no rules for the cables farther than 6 feet from the access hole. However, use common sense. I would not recommend that you try to improve this situation. It's fine as is, and you may create additional problems.

Bob C, I haven't forgotten about you (yet). I'll address it when I get access to the tools I need.
 
  #6  
Old 07-09-04, 05:28 PM
Bob C
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John, any luck on the capacity? Appreciate all of your help.

An electrician once told me that 100 amp service in a sense can be pulling 200 amps as each power line coming in can pull up to 100 amps. Does the 100 amp breaker allow this to happen? Does the breaker only trip if more than 100 amps are being pulled on one of the power runs. Don't know if I am explaining this properly, hope you know what I mean.

Another thing he said was that you can wire a three prong outlet in a two wire situation by connecting a wire from the neutral to the ground in the receptacle. As my house has no separate ground bar and all of the grounds and neutrals are on the same bar. Isn't connecting the ground and the neutral at the receptacle the same as running a third wire from the ground on the receptacle to the panel box bar where all neutrals and grounds are tied together anyway?

Thanks
 
  #7  
Old 07-09-04, 05:54 PM
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Bob, thanks for reminding me. I had finally forgotten about you.

Unfortunately, the 3-ton air conditioner and electric dryer combine to make 100 amp service insufficient to also support the addition of an electric range. Without the range, your demand load is 81 amps, within the capacity of your 100-amp service. But the range would push your demand load to 114 amps, too much.

Isn't 3 tons of A/C a lot for a 1400 square foot home?

Too much attention is paid to this notion of getting 200 amps from 100 amp service. You could get 200 amps if all your loads were 120 volts. Unfortunately, in most homes, the really big loads, which create the majority of the demand, are 240-volt loads. This whole topic just confuses most people, and it only comes up as an academic thought exercise. It is rarely a useful concept, and often distracts from what's important.

Another thing he said was that you can wire a three prong outlet in a two wire situation by connecting a wire from the neutral to the ground in the receptacle.
This is clearly the worst electrical advice you will ever receive. And any electrician who gives this advice should not be trusted to do any work in your home. If he's willing to suggest this extremely hazardous wiring method, what the hell might he be doing to your electrical system???

Isn't connecting the ground and the neutral at the receptacle the same as running a third wire from the ground on the receptacle to the panel box bar where all neutrals and grounds are tied together anyway?
This is one of the most alluring fallacies in household electrical wiring. And it sounds so reasonable, doesn't it? Refuting this terrible idea would take a 10,000 word essay (or better yet, a book on grounding), and it's almost dinner time. Maybe another time.
 
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